1. Field of the Invention
The present invention relates to equipment and apparatus used in the manufacture of electronic devices including semiconductor devices, MEM devices, and other devices used in data manipulation, storage, and display, for example and not by way of limitation. In particular, the invention pertains to the use of yttrium oxide-comprising protective layers which are applied to a surface of apparatus, such as process chamber liners, gas feed plates, substrate support pedestals, and electrostatic chucks, valves, and similar components which are likely to be exposed to a corrosive environment. The presence of the protective layer protects an underlying material, which makes up a portion of the body, from the corrosive environment.
2. Description of the Background Art
Corrosion (including erosion) resistance is a critical property for components used in processing chambers where corrosive environments are present. This is especially true where high-energy plasma is present and electrical driving force may be combined with chemical driving force to act upon the surface of components present in the environment.
Process chambers and component apparatus present within processing chambers which are used in the fabrication of electronic devices and MEMS are frequently constructed from aluminum and aluminum alloys. Surfaces of a process chamber and component apparatus present within the chamber are frequently anodized to provide a degree of protection from the corrosive environment. However, the integrity of the anodization layer may be deteriorated by impurities in the aluminum or aluminum alloy, so that corrosion begins to occur early, shortening the life span of the protective coating. Ceramic materials of various compositions have been used in place of the aluminum oxide layer mentioned above, and have been used over the surface of the anodized layer to improve the protection of the underlying aluminum-based materials. However, the protective layer continues to be deteriorated by impurities in the aluminum or aluminum alloy, even though the life span of the protective layer is extended. More recently, high purity aluminum alloy materials have been developed which reduce the tendency of the protective layer or layers to fail. However, the high purity aluminum alloy materials tend to be expensive.
Yttrium oxide is a ceramic material which has shown considerable promise in the protection of aluminum and aluminum alloy surfaces which are exposed to fluorine-containing plasmas of the kind used in the fabrication of semiconductor devices. In U.S. application Ser. No. 10/075,967, the parent application of the present continuation-in part application, it is disclosed that a yttrium oxide coating applied over an anodized surface of a high purity aluminum alloy process chamber surface or process component surface produces excellent corrosion protection. In addition, the evaluation of pure ceramic materials used as apparatus components has illustrated that a long lifetime for the component may be achieved. However, there remains a need for a protective layer or coating which can protect the more standard high temperature aluminum-based materials, such as those in the 2000 series and the 5000 to 7000 series.
Japanese Patent Application No. HEI 3[1991]-287797, of Shinji Inazawa et al., published Dec. 18, 1991, discloses a corrosion-resistant ceramic film useful in protecting electric wires or component materials fabricated from aluminum or aluminum alloy from corrosive vapors or low melting point metals and highly corrosive inorganic halides and organic metal compounds. The corrosion-resistant ceramic film is formed by first producing an oxidized film formed by the anodic oxidation of the surface of aluminum or an aluminum alloy. Subsequently, the oxidized film is submersed in a solution to provide impregnation with at least one type of ion selected from the group consisting of chromium ions, yttrium ions, zirconium ions, and magnesium ions. The corrosion-resistant protective film surrounding an electric wire is produced by firing in an oxygen gas stream at 500° C. The particular example illustrating the concept is a coating on pure aluminum wire, where the ions in the anodized film are created using chromium trioxide aqueous solution.
In a further embodiment of the above-described technology, the corrosion-resistant material described above is further submersed in a solution of a ceramic precursor consisting of a polymerizable organic metal compound, followed by heat treatment to form an outer insulation film of oxide ceramic.
In U.S. Pat. No. 5,366,585, to Robertson et al., issued Nov. 3, 1994, a plasma processing chamber is described which includes a ceramic barrier material, preferably in the range of 130 μm to 250 μm thick, for protecting metallic walls of the process chamber from attack by the plasma. The ceramic material is said to typically comprise aluminum oxide, although the oxide and fluoride forms of aluminum, magnesium, and tantalum are mentioned. Although free-standing liners are described, protective ceramic layers which are deposited without consuming the underlying metal (aluminum) substrate are also described. For example, flame-sprayed or plasma-sprayed aluminum oxide is discussed.
U.S. Pat. No. 5,798,016, to Oehrlein et al., issued Aug. 25, 1998, describes a method and apparatus for etching semiconductor devices where undesirable deposition of films on internal surfaces of the apparatus are prevented using a heatable liner or process chamber wall. The heated liner or chamber wall may be constructed from a “wide variety of materials, for example, ceramics, aluminum, steel, and/or quartz. Aluminum is the preferred material because it is easy to machine.” However, since aluminum is reactive with a number of plasmas, it is recommended that “aluminum oxide or a coating thereof be disposed on the liner or chamber walls”, because aluminum oxide tends to be chemically inert. In addition to the materials used to construct the liner and/or chamber walls, a protective coating may be applied to the surfaces of the liner and/or chamber walls. Examples which are given include Al2O3, Sc2O3, or Y2O3.
U.S. Patent Application Publication No. US 2001/0003271A1, of Otsuki, published Jun. 14, 2001, describes a processing apparatus for semiconductor wafers, where the process may include a plasma, in which a film of Al2O3, or Al2O3 and Y2O3, is formed on an inner wall surface of the chamber and on those exposed surfaces of the members within the chamber which require a high corrosion resistance and insulating property. An example is given of a processing chamber where a base material of the chamber may be a ceramic material (Al2O3, SiO2, AlN, etc.), aluminum, or stainless steel, metal or metal alloy, which has a sprayed film over the base material. The sprayed film may contain an oxide of Y, Sc, La, Ce, Eu, Dy, or the like, or fluoride of one of these metals. The film may be made of a compound of a III-a element of the periodic table, such as Y2O3 The film may substantially comprise Al2O3 and Y203. A sprayed film of yttrium-aluminum-garnet (YAG) is also mentioned. The sprayed film thickness is said to range from 50 μm to 300 μm. There is no description of the manner in which the sprayed film is applied. There is no description of the condition of the interface between the base material and the film. Further, there is no description of metal impurity concentrations in the sprayed film or loose particles which may be present on the film surface. This is important because the condition of the interface between the base material and the sprayed film will have a significant effect on the lifetime of the process chamber. The metal impurity content of the sprayed film and the loose particles present on the film surface will have a significant effect on the product yield for product produced in the process chamber, as will be addressed by applicants during the description of their invention.
U.S. Pat. No. 6,352,611, to Han et al., issued Mar. 5, 2002, describes a dielectric window of a reactor chamber where substrates are processed in a plasma of a processing gas. A ceramic composition of matter used to produce a process kit and a dielectric window preferably contains a ceramic compound (e.g., Al2O3) and an oxide of a Group IIIB metal (e.g., Y2O3). The ceramic compound may be selected from silicon carbide, silicon nitride, boron carbide, boron nitride, aluminum nitride, aluminum oxide, and mixtures thereof; however, aluminum oxide is said to be available in a pure form which does not outgas. The Group IIIB metal may be selected from the group consisting of scandium, yttrium, the cerium subgroup, and the yttrium subgroup; however, yttrium is preferred, with the oxide being yttrium oxide. The preferred process for forming or producing the dielectric member is by thermal processing of a powdered raw mixture comprising the ceramic compound, the oxide of a Group IIIB metal, a suitable additive agent, and a suitable binder agent.
U.S. Pat. No. 6,565,984, to Wu et al., issued May 20, 2003, describes the use of a high purity aluminum alloy to form process chambers and processing components used for plasma processing. The high purity aluminum alloy is protected by an anodization layer. By controlling the composition of the alloy and the size of particulate inclusions in the alloy, an improved performance is achieved with respect to corrosion resistance for the alloy protected by an anodization layer.
The above-described references are only a few of the background references available. However, in view of the existing art known to applicants, there is still a need for a protective layer or coating which can protect the more standard high temperature aluminum-based materials, such as those in the 2000 series or 5000 to 7000 series, where the alloy composition and size of particulate inclusions can cause problems of the kind described in the Wu et al. reference. The problems exist with respect to a protective aluminum oxide coating, whether formed by anodization or by spray application. Problems similar to those occurring in the aluminum oxide coatings occur when other protective spray coatings, such as sprayed films containing oxides of Y, Sc, La, Ce, Eu, Dy, or the like, or fluorides of one of these metals, such as Y2O3 or yttrium-aluminum-garnet (YAG), are applied over a surface of the 2000 series or 5000 to 7000 series of aluminum alloys. These aluminum alloys are very desirable as substrates for process chamber and component fabrication due to availability and cost, as well as performance properties not related to plasma corrosion resistance, so ability to apply a protective layer with an extended lifetime over these alloys is important.